Compressed air supply devices perform numerous tasks in rail vehicles and commercial vehicles. These include, in particular, the supply of the brake system and further compressed air consumers with dry purified compressed air. The compressed air which is used by the compressed air consumers is provided primarily by a compressor and is usually prepared in a compressed air preparation device. During the preparation, the compressed air is dried, and oil and dirt particles are removed from the compressed air before it is fed to the compressed air consumers.
During starting up of compressors against pressure, high moments have to be overcome. As a result, great mechanical loads can be produced and, in particular, the drive of the compressor has to be of sufficiently great dimensions. Specifically at low temperatures, in the case of an insufficient design, the problem can occur that the compressor does not start up against the pressure. In the case of oil-lubricated compressors, furthermore, the problem can exist that, during starting up under load, the lubrication is not yet sufficient. In order to prevent starting up under load, it is desirable to lower the pressure at the outlet of the compressor after shutdown to such an extent that the compressor can start without a back pressure or only with a reduced back pressure during restarting.
In this context, for example, DE 10 2006 043 863 A1 and DE 30 42 069 A1 in each case disclose a compressor with an integrated venting apparatus, in order that the compressor can start up as far as possible without back pressure.
Furthermore, for example, DE 81 09 217 U1 and DE 10 2010 054 712 A1 in each case disclose a compressed air supply device, the compressed air line of which between the compressor and the air dryer can be vented via an additionally provided venting line with an additionally provided venting valve device, in order to make starting up of the compressor as far as possible without back pressure possible.